Principles of naval engineering - Historic Naval Ships Association

Chapter 17. -COMPRESSED AIR PLANTSof liquid and ready to repeat the cycle which takesplace twice in each revolution.A small amount of seal water must be constantlysupplied to the compressor to make upfor that which is carried over with the compressedair. The water which is carried over withthe compressed air is removed in a refrigeration-typedehydrator.AIR COMPRESSOR MAINTENANCEMinimum requirements for the performanceof inspections and maintenance on high pressureair plants are shown on the maintenance indexpage figure 17-12.It is the responsibility of the engineer officerto determine if the condition of the equipment,hours of service, or operating conditionsnecessitate more frequent inspections and tests.Details for outline tests and inspections may beobtained from the appropriate manufacturer'sinstruction book or from the Naval Ships TechnicalManual.SAFETY PRECAUTIONSThere are many hazards associated with theprocess of air compression. Serious explosionshave occurred in high pressure air systemsbecause of a diesel effect. 2 Ignition temperaturesmay result from rapid pressurizationof a low pressure dead end portion of thepiping system, malfunctioning of compressoraftercoolers, leaky or dirty valves, and manyother causes. Every precaution must be taken tohave only clean, dry air at the compressor inlet.Air compressor accidents have also beencaused by improper maintenance proceduressuch as disconnecting parts while they areunder pressure, replacing parts with unitsdesigned for lower pressures, and installingstop valves or check valves in improper locations.Improper operating procedures havealso caused air compressor accidents, withresulting serious injury to personnel anddamage to equipment.In order to minimize the hazards inherentin the process of compression and in the useof compressed air, all safety precautionsoutlined in the manufacturers' technical manualand in the Naval Ships Technical Manualmust be strictly observed.2 A diesel engine operates bytakinginair, compressingit, and then injecting fuel into the cylinders, wherethe fuel is ignited by the heat of compression. Thesame effect (normally called the diesel effect ) canoccur in hydropneumatic machinery and in air, oxygen,or other gas systems, if even a very small amount of"fuel"— a smear of oil, for example, or a single cottonthread— is present to be ignited by the heat ofcompression.449